Re: LG 47LN578V - Brief Backlight flash on power up.

Apologies for the delay, University Today

I'm going to rip these strips out to test the leds individually and then De-Cap any that won't light up to see how they are constructed. It appears the lens assembly is held on by 3 dabs of what appears to be epoxy, I will try a couple of methods for de-capping them and see which is the least destructive whilst getting some high resolution photos in the process

What I know so far:
There are 54 LEDs on boards labelled ROW2.1 Rev 0.7 L1 and ROW2.1 Rev...

Re: LG 47LN578V - Brief Backlight flash on power up.



Timing!
Ah, That makes sense.

Thank you very much for your help. I shall see if I this potential backlight comes good, if not I think it may be destined for the scrap heap....

Re: LG 47LN578V - Brief Backlight flash on power up.

Thought I may as well tear into it, in for a penny in for a pound =)

I set up my DSLR with an 8 second exposure time and switched the TV on so I could easily see if any LEDs weren't coming on, the result is quite interesting...

On two of LED strips there's one LED out... I'm assuming they are in series so surely these must me shorted? And then there's three entire rows that aren't lighting up. However one of the rows isn't in adjacent.

At the very least it's a cool photo!...

Re: LG 47LN578V - Brief Backlight flash on power up.

Hi Budm,

Cheers for the diagram

I have done the voltage measurements as requested and these are my findings:
Cap set 1: 0V, Quickly rises to 160V then slowly discharges after backlight has turned off
Cap set 2: 0V, Quickly rises to 96V then slowly discharges after backlight has turned off

I'm guessing this points to a backlight strip fault? Intuition tells me that the strip powered by the circuit containing "Cap set 2" has a short or is at the very least taking excess...

Re: LG 47LN578V - Brief Backlight flash on power up.

Hi Budm,
Thank you for taking the time to look at my thread
I hope these photos prove adequate....

Hello everyone!

I'm trying to repair an LG smart TV, 47LN578V and have so far come to conclusion that the PSU has a fault but would like a second opinion.

[B]Symptoms[/B]
Powering TV on causes the screen to come on briefly with LG logo then the backlight goes out, the smart functions of the set continue to function and the TV can be controlled both via the remote and over the android application.
Shining a light into the screen allowed me to view the android application pairing key.

[B]Measurements[/B]
Main, Large, Cap: 394V...

Re: New Members - please post your introductions here

Hello from the north of England!

I'm Tezz, My first computer was a BBC Micro Model B and I love music, programming and pulling things to bits.

I play Bass Guitar professionally and am currently studying for a music degree